A high precision numerical algorithm MVPPM (multi-viscous-fluid piecewise parabolic method) is proposed and applied to study the multi-viscous-fluid dynamics problems. Three planar jelly experiments with periodic cosine perturbation on the initial interface have been conducted and numerically simulated by MVPPM. Good agreement between experimental and numerical results has been achieved, including the shape of jelly interface, the displacements of front face of jelly layer, bubble top and spike head. The effects of initial conditions (including amplitude and wave length of perturbation, thickness of jelly layer, etc.) on the evolution of the jelly interface have been numerically analyzed. It is found that the key affecting factors are the perturbation amplitude and thickness of jelly layer. The hydrodynamic instability on double planar jelly layers driven by explosion has been investigated numerically to examine their laws of evolution, and an interesting phenomenon is observed.